This invention relates to a digital communication device, and particularly, to one useful for providing a coded number or word for identifying a mobile article.
In manufacturing facilities employing so-called flexible machining systems, mobile pallets are used to automatically transport workpieces between work stations. In such facilities, it is frequently desirable for the pallets to be identified by the work station so that the machine operating on the workpiece can execute stored instructions for carrying out desired steps for a particular workpiece or type of workpiece, Such an identification feature would also be useful for material control purposes even when each workpiece is to be processed in identical fashion. A preferred system for identifying pallets or other articles would avoid the use of electrical contacts between the work station and the mobile device since such systems are subject to reliability problems. Since the pallets or other mobile articles are designed to be completely self-contained, it is further desirable to operate such an identification system using low power electrical supply sources such as storage batteries.
In accordance with this invention, a digitally operated identification transponder is provided which is adapted to travel on a mobile device such as a pallet which responds to a flash of light transmitted by an interrogator device. The signal from the interrogator causes the transponder to repeatedly transmit a stored identification code using light pulses which are received and interpreted by the interrogator device. The transponder provides a binary identification digital word which can be reprogrammed as desired. The transponder in accordance with this invention employs means for preventing ambient light from being interpreted as an interrogating signal and is further designed to minimize battery current drain when not operating to provide an identification signal. The system further incorporates a battery checking system and means for communicating a signal indicating low battery voltage.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawing.